Step 1. It is similar like in loop, but you have to know (or make an assumption) the pressure (head) on the start of the branch and at the end of the branch and based on pressure (head) change from start to the end of branch you can calculate the flow.

Step 2. Now that calculated flow is influencing the pressure on the start of the branch, because flow in connecting pipe, so it (pressure, head) has to be recalculated based on the flow through the branch and other flow that goes by (total flow is the flow through all branches).

When you have that new pressure on the start of the branch, go back to step 1. and calculate flow again, go to step 2, and loop until the pressure change is small enough.

Dear Mr. Administrator,
I've read your explanation repeatedly. Overall, i know what you mean. But i'm still not exactly understand the step by step. Can you exlpain to me again, including illustration (use picture). If you explain with illustration i hope i will more understand.

Your solution (step by step) is similar with Newton-Raphson method. Is that true?
Thanks..